Jel­ly­fish In­va­sion

The world’s oceans have been ex­pe­ri­enc­ing enor­mous blooms of jel­ly­fish, ap­par­ently caused by over­fish­ing, de­clin­ing water qual­ity and ris­ing sea tem­per­a­tures. Now, sci­en­tists are try­ing to de­ter­mine if these out­breaks could rep­re­sent a “new nor­mal” in whi

Element - - Global Bulletin - By Richard Stone

Among the spine­less crea­tures of the world, the No­mura’s jel­ly­fish is a mon­ster to be reck­oned with. It’s the size of a re­frig­er­a­tor — imag­ine a Frigidaire Gallery Pre­miere rather than a ho­tel mini­bar — and can ex­ceed 450 pounds. For decades the hulk­ing me­dusa was rarely en­coun­tered in its stomp­ing grounds, the Sea of Ja­pan. Only three times dur­ing the en­tire 20th cen­tury did num­bers of the No­mura’s swell to such gi­gan­tic pro­por­tions that they se­ri­ously clogged fish­ing nets. Then some­thing changed. Since 2002, the pop­u­la­tion has ex­ploded six times. In 2005 the Sea of Ja­pan brimmed with 20 bil­lion jel­ly­fish, hit­ting fish­eries with 30 bil­lion yen in losses.

Why has the No­mura’s jel­ly­fish be­come a re­cur­ring nightmare? The an­swer could por­tend trou­ble for the world’s oceans. In re­cent years, pop­u­la­tions of sev­eral jel­ly­fish species have made in­roads at the ex­pense of their main com­peti­tor — fish — in a num­ber of regions, in­clud­ing the Yel­low Sea, the Gulf of Mex­ico, and the Black Sea. Over­fish­ing and de­te­ri­o­rat­ing coastal water qual­ity are chief sus­pects in the rise of jel­lies. Global warm­ing may be adding fuel to the fire by mak­ing more food avail­able to jel­ly­fish and open­ing up new habi­tat. Now, re­searchers fear, con­di­tions are be­com­ing so bad that some ecosys­tems could be ap­proach­ing a tip­ping point in which jel­ly­fish sup­plant fish.

Es­sen­tial to thwart­ing any po­ten­tial jel­ly­fish takeover is a bet­ter un­der­stand­ing of the complicated dy­nam­ics be­tween fish and jel­ly­fish. Jel­ly­fish are a nor­mal el­e­ment of ma­rine ecosys­tems. Fish and jel­ly­fish both com­pete for plank­ton. The preda­tors keep each other in check: 124 kinds of fish species and 34 other species, in­clud­ing leatherback tur­tles, are known to dine on jel­ly­fish, while jel­lies prey on fish eggs and, oc­ca­sion­ally, on fish them­selves. Ju­ve­nile fish of some species take refuge amid ten­ta­cles and eat jel­ly­fish par­a­sites. Fish and jel­ly­fish “in­ter­act in com­plex ways,” says Kylie Pitt, an ecol­o­gist at Grif­fith Univer­sity in Australia.

Over­fish­ing can throw this com­plex re­la­tion­ship out of kil­ter. By re­mov­ing a curb on jel­ly­fish pop­u­la­tion growth, over­fish­ing “opens up eco­log­i­cal space for jel­ly­fish,” says An­thony Richard­son, an ecol­o­gist at CSIRO Ma­rine and At­mo­spheric Re­search in Cleve­land, Australia. And as jel­ly­fish flour­ish, he says, their pre­da­tion on fish eggs takes a heav­ier toll on bat­tered fish stocks.

“When an ecosys­tem is dom­i­nated by jel­ly­fish, fish will mostly dis­ap­pear,” says ecol­o­gist Sun Song, di­rec­tor of the In­sti­tute of Oceanol­ogy in Qing­dao, China. “Once that hap­pens, there is al­most no method to deal with it.”

To­tal jelly dom­i­na­tion would be like turn­ing back the clock to the Pre­cam­brian world, more than 550 mil­lion years ago, when the an­ces­tors of jel­ly­fish ruled the seas.

Sun and oth­ers are rac­ing to get a han­dle on the like­li­hood of such a ma­rine melt­down com­ing true. Like their foe, the sub­ject is slip­pery. It’s an enigma, for starters, why par­tic­u­lar jel­ly­fish run ram­pant. The trou­ble­mak­ers “are only a small frac­tion of the sev­eral thou­sand species of jel­ly­fish out there,” says Richard­son. These uber-jel­lies re­pro­duce like mad, grow fast, eat most any­thing, and can with­stand poor water qual­ity. They are tough, Richard­son says —“like cock­roaches.”

The big ques­tion is whether these cock­roaches of the sea are poised to hi­jack ma­rine ecosys­tems. There’s anec­do­tal ev­i­dence that jel­ly­fish blooms are be­com­ing more fre­quent. But there are also cases in which jel­ly­fish gained the up­per hand on an ecosys­tem, only to sud­denly re­lin­quish it. For in­stance, biomass of Chrysaora jel­ly­fish in the east Ber­ing Sea rose sharply dur­ing the 1990s and peaked in 2000. Chrysaora then crashed and sta­bi­lized af­ter 2001, ap­par­ently due to a com­bi­na­tion of warmer sea tem­per­a­tures and a re­bound in num­bers of wall­eye pol­lock, a com­peti­tor for zoo­plank­ton.

The jury is out on whether other jelly-blighted wa­ters can re­gain eco­log­i­cal bal­ance as quickly as the Ber­ing Sea did. For that rea­son, says Pitt, no one can say for sure whether se­vere jel­ly­fish blooms are a pass­ing re­gional phe­nom­e­non or a global scourge re­quir­ing ur­gent mea­sures to combat their spread.

Pitt is one of a small band of jel­ly­fish re­searchers hop­ing to set­tle that ques­tion. With sup­port from the Na­tional Cen­ter for Eco­log­i­cal Anal­y­sis and Synthesis in Santa Bar­bara, Calif., she and her col­leagues on the cen­ter’s Jel­ly­fish Work­ing Group are gath­er­ing up datasets from around the world on jel­ly­fish blooms. They ex­pect to have a global picture — and be able to take the mea­sure of their foe — in about a year, Pitt says.

Jel­ly­fish clearly have an im­pact on hu­man ac­tiv­ity. Be­sides foul­ing fish­ing nets, they in­vade fish farms, block cool­ing in­takes at coastal power plants, and force beach clo­sures. Some jel­lies pose a mor­tal threat. Dozens of Jel­ly­fish blooms can be caused by eu­troph­i­ca­tion, which can cre­ate dead zones around mouths of rivers.

Global warm­ing may al­low deadly jel­ly­fish, now mostly found in trop­i­cal and sub­trop­i­cal wa­ters, to con­quer new turf in tem­per­ate wa­ters as sea sur­face tem­per­a­tures rise, warns Richard­son. “It’s very likely that ven­omous jel­ly­fish will move to­ward the poles,” he says.

The UK’S old­est en­vi­ron­men­tal char­ity is to close be­cause its in­come has been hit by cuts to lo­cal au­thor­ity bud­gets. En­vi­ron­men­tal Pro­tec­tion UK, orig­i­nally es­tab­lished in 1898 as the Coal Smoke Abate­ment So­ci­ety, pro­vides ex­per­tise, ad­vice and anal­y­sis on air qual­ity and land, waste and noise is­sues. It says it will stop func­tion­ing as a fully staffed and funded or­gan­i­sa­tion in March 2012. How­ever, it hopes that it can carry on with at least some of its work on a vol­un­tary ba­sis. Pres­sure from en­vi­ron­men­tal groups has prompted US Pres­i­dent Barack Obama to halt the progress of the Key­stone XL Pipe­line. If built, the pipe­line would carry 700,000 bar­rels of crude oil a day from Canada’s Al­berta oil sands to re­finer­ies along the U.S. Gulf of Mex­ico coast. The pipe­line com­pany, Tran­scanada, are not back­ing down, and plan to sub­mit a new ap­pli­ca­tion for an al­ter­nate pipe­line route.

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